Process for the manufacture of dialkyl sulfides



Oct- 20, 1953 w. A. scHULzE ET A1. 2,656,392

PROCESS FOR THE MANUFACTURE OF DIALKYL SULFIDES Filed Dec. 15, 1948 U3v:moz L NouvNouovui t] 1Q :moz NouvNolmvaA :moz o sNlHsvM N *2 l -f A3Noz Nom/waasA N m a BNOZ a N Nouova I *ln 9 l a 0 INVENToRs v w.A.scHu|zE 1 -m BY w.w.cRoucH Y D @Q7/M 4 fm ATTORNEYS Patented Oct. 20, 1953PROCESS FOR THE MANUFACTURE OF DIALKYL SULFIDES Walter A. Schulze andWillie W. Crouch, Bartlesville, Okla., assignors to Phillips PetroleumCompany, a corporation of Delaware Application December 13, 1948, SerialNo. 65,008

10 Claims.

This invention relates to dialkyl disuldes. In one of its more specificaspects, it relates to the manufacture of dialkyl disuldes by theoxidation of low molecular weight mercaptans in an aromatic hydrocarbonsolvent medium.

In the past, small concentrations of mercaptans, such as those naturallyoccurring in petroleum oils, have been oxidized to disullides andpolysulfides by various methods. For example, in the manufacture ofgasoline, the oxidation of contaminating mercaptans to disulfldes haslong been practiced for the purpose of eliminating their obnoxious odor.However, in such instances, the concentration of mercaptans is very,very small, usually about 0.01 to 0.03 per cent, and the qantity ofdisuldes produced by their oxidation is even smaller. Obviously suchoperations do not afford a commercial source of disuldes since recoveryof these exceedingly small amounts is uneconomical and impractical dueto the enormous throughput necessary.

An obvious method for the production of disuldes would appear to lie infortifying the gasoline with a suicient amount of the desired mercaptanto provide a concentration of at least 5 to l0 per cent, or moredesirably 20 to 40 per cent, and oxidizing the said mercaptan content todisulfide, thus providing sufficiently great dsulflde concentration thatrecovery could be carried out economically. However, attempts to op- Itwill be observed that in the first reaction, i. e., according toEquation l, half of the mercaptan is converted to cuprous mercaptidewhich is then transformed to disulfide in the second reaction, Equation2, by further action of cupric ions. For Reaction 2 to proceedsatisfactorly, it is necessary for the cuprous mercaptide to remaindissolved in the solution in order that adequate contacting with theoxidizing agent may occur. In fact, for the reaction to proceed, it isrequired that a finite concentration of cuprous.

mercaptide be built up and maintained in the solution. However, whenattempting to operate with higher concentrations of mercaptans of lowmolecular weight or mercaptans of tertiary configuration, in gasolinethe cuprous mercaptides formed being but slightly soluble therein,precipitate from the system. Thus, Reaction 2 either does not take placeor proceeds at a greatly reduced rate. Furthermore, the reduction in theconcentration of copper and attendant reduction in pH of the systemcaused by the precipitation of the cuprous mercaptides effects a seriousreduction in oxidation potential, even though provision is made forregeneration of the soluble cuprous copper to cupric copper. As theoxidation potential is reduced, Reaction l also proceeds at acorrespondingly reduced rate. Thus, such a procedure is generallyunsatisfactory for disulfide manufacture.

An object of this invention is to provide a process whereby mercaptansmay be oxidized to dialkyl disuldes.

Another object is to provide an economical and rapid process for theproduction of dialkyl disuldes.

Another object is to provide a continuous process for the oxidation ofmercaptans to dialkyl disuldes.

Still another Objectis to provide a process for the manufacture ofdialkyl disulides by the oxidation of mercaptans in an aromatichydrocarbon medium.

Another object is to provide a process for the manufacture of dialkyldisuliides by the oxidation of low molecular weight mercaptans, thecuprous mercaptides formed from said mercaptans, which are intermediateproducts, being insoluble in aliphatic hydrocarbons.

Another object is to provide a process for the manufacture of dialkyldisulfides by the oxidation of low molecular weight mercaptans in anaromatic medium.

Another object is to provide a process for the manufacture of dialkyldisuldes wherein a high oxidation potential is maintained.

Another object is to provide a process for manufacture of dialkyldisuldes Vwherein substantially all of the cuprous mercaptideintermediate product is maintained in solution.

Another object of this invention is to provide a process for themanufacture of dialkyl disuldes wherein the reaction mixture contains ahigh percentage of cuprous mercaptide.

Further objects and advantages of our inven- *21011 W111 be apparent toone skiued ,in the art 3 from the accompanying disclosure anddiscussion.

We have discovered a process whereby mercaptans, particularly lowmolecular weight mercaptans whose corresponding cuprous mercaptides areinsoluble in aliphatic hydrocarbons, may be oxidized to thecorresponding dialkyl disuldes in aromatic hydrocarbon media by theaction of an aqueous solution of cupric copper ions thereby eliminatingor substantially reducing the aforementioned diftioulties. In accordancewith one method for the practice of our invention, a mercaptan, whichmay be primary, secondary, or tertiary and which may contain as many as12 carbon atoms per molecule, but preferably not more than carbon atomsper rnol'e'c'zule,V may be oxidized to the corresponding dialkylvdisulfide in a continuous process with,V a high. degree Aof conversion,often substantially quantitative. By our process, the oxidation iscarried out in a medium comprising an aromatic hydrocarbon solvent ofthe singleA ring type Such as benzene, or alkyl substituted benzenessuch as toluene, cumene, xylene, ethylbenzene, and the like, containingat least 80 per cent aromatics in which cu'prous mercaptide in theamounts produced is soluble. When operating in this manner, a stream ofmercaptan dissolved in the solvent is fed toa reactor wherein it iscontacted with an aqueous solution of cupric copper ions underconditions for substantially complete oxidation of the mercaptan todialkyi disulfide. A suitable ratio of the mercaptan to the aromaticsolvent in the feed stream to the reactor is 1:2 to 1:5, how'- ever,under many circumstances it may be preferable to use ratios of 1:3 to1:4. Desirable ratios of aqueous cupric copper solution tomercaptan-aromatic hydrocarbon solution in the reactor are 1:1 to l0; 1,however, preferred ratios are in the range of 6:1 to 8:1. A portion ofthe reaction mixture, i.L e., the material taken from the reactorcontaining dialkyl disulde, aromatic, and aqueous cupric copper, iscontinuously circulated from, the reactor through a separating. chamberfrom which theaqueous phase is continuously removed and subjected totreatment for regeneration of the cupric ions, for example, by blowingwith an oxygen-containing gas, after which. the solution containing theregenerated cupric ions isjreturned to thev reactor. The organic phasecontaining dialkyl disulfide. and aromatic hydrocarbon, which` isremovedalong with the aqueous phase and separated therefrom, is divided'into a major and, minor portion, the major portion being recycled to thereaction zone and the minor portion being discharged to a fractionaldistillation system Where the solvent is removed for recycling and thedialkyldisulfide removed as prod-V uct. Ihe minor portion of the organicphase comprising the product take off, and the mercaptan-aromaticsolution feed to the reactor will be of substantially equal volume whena steady state has been established. Suitable conditions within thereactor for carrying out thisreaction are temperatures in the range of50y to 200 F. and preferably temperatures in the range of 7.0 to 140 F.However, when operating with particularly refractory mercaptans, it maybe desirable to maintain a4 somewhat higher temperature than that givenas a preferred range, say between 140 and 175 F. Pressure 'does notordinarily affect the reaction to any great extent and one which willmaintain the liquid phase may be readily selected by one skilledin theart.

By so operating our process several important advantages are gained;One'such advantage lies in the use of the aromatic solvent medium inwhich the oxidation is carried out, said solvent medium being of such anature that the cuprous mercaptide formed as an intermediate in thereaction, is maintained in solution. Thus, the cupric ions areconstantly in contact with the dissolved mercaptide and its conversionto dialkyl disulfide is thus rendered substantially complete.

Our process also provides for the maintenance of a high oxidationpotential, and a substantially constant concentration of copper in thesystem. 'l'hus,r byY continuous circulation of the aqueous coppersolution to the regeneration systeml the concentration of cupric ions ismaintained at an optimum level and the pH of the system iscorrespondingly upheld. If the cuprous mercaptide was allowed toprecipitate, the acid content of the reaction mixture would increase andthe pH would go down. Thus, since a high oxidation potential isdependent on a high pH, the reaction would be brought to a standstill.The requisite high potential is further insured by the high internalrecycle of organic constituents. The rate of mercaptan feed may beregulated in a manner such that substantially complete oxidation iseffected and at the same time separation and regneration of the coppersolution may be carried out at a much higher rate than the throughput ofmercaptan. For example, 50 to 200 volumes of copper solution may beremoved and regenerated for each volume of mercaptan fed and dialkyldisulfide solution removed.

The oxidizing copper solution used in our process comprises an aqueoussolution of cupric copper in the presence of a chloride ionconcentration equivalent to that of a l0 to 20 mol per cent sodiumchloride solution. A cupric copper concentration may vary from about 3to about 14 mol per cent althoughV intermediate concentrations of from 5to 10l mol per cent are ordinarily preferred The rate of circulation ofthe above copper solution to regeneration will vary, depending upon therate of regeneration, mercaptan feed, and other-features. We have foundthat in many instances a circulation of about 50 to 200 volumes ofcopper solution to regeneration for each vol-l urne ofV mercaptansolution fed to the reaction zone gives satisfactory results. However,variationsin concentration of mercaptan in the feed streamy williniiuence this rate considerably. In any case, the rate of circulationand regeneration should be such` that the oxidation potential Within thereaction zone, measured against saturatedy calomel, is maintainedbetween about 375 and 500millivolts.

A further understanding of some of the many aspects of` our-inventionmay be had by referring to the attached drawing, which is a schematicflow diagram, in combination with the following description. Variousadditionalvalves, pumps, and othen conventional equipment necessary forthe practice of this invention will be familiar to one skilled in theart and have been omitted from the drawing for the-sake of clarity. Thedescription of the drawing provides one method of operating our process,however, it is understood that while this is representative in generalof our process, various minor changes may be made in adapting it to thevarious conditions within the scope of the invention.

Refer now to the drawing. A solution oftertiary octyl mercaptan intoluene is agitated with a major portion, i. e., a portion comprisingmore. than one half` of the total reactionmixture,

of an aqueous solution of cupric copper ionsin reaction zone I. A streamof this mixture is continuously removed via line 2 and pump 3 toseparation zone 4 where the aqueous copper solution separates by gravityand is conveyed through line 5 to regenerating zone 6. In this zone, airfrom line 'I is blown through the solution to oxidize the reduced copperand to regenerate the cupric ions. We have generally preferred tointroduce the air into the copper solution through a porous tube or disc8 whereby moreadequate contacting is eected. However, any suitablemethod for thoroughly diffusing the air through the copper solution andeffecting good regeneration may be used. A suitable regenerationtemperature may be room temperature, however, this is not critical. Theregeneration rone 6 is vented through line 9 for removal of theregeneration gas. Vapor recovery means, not shown, may be utilized inconjunction with line 9 to prevent loss of solvent which may have beenentrained in the copper solution. After regeneration, the cupricsolution is returned to reaction zone I via lines I and 25. A majorportion of the organic phase in the separation zone is constantlyreturned to the reaction zone through line I I. A minor portion of thisphase which is the product stream is passed via lines II and I2 towashing Zone I3 where entrained copper is removed by caustic treatment.The product stream is removed from washing zone I3 via line I4 and ispassed to fractionation zone I for removal of toluene overhead, and fromthence via line I6 to fractional distillation zone I'I for finaldistillation, preferably under reduced pressure. The product, ditertiaryoctyl disulfide is removed from fractional distillation zone I'I vialine I8. The toluene recovered in zone I5 is conveyed through recyclelines and 24 to mixing zone 2| where it is admixed with tertiary octylmercaptan introduced through line 22 the admixture then being charged toreaction zone I Via line 23.

While the solvent and copper solutions employed in our process are notconsumed and eiiicient recycling makes possible continuous operation forconsiderable periods of time without additions of these materials,provision is made for solvent makeup through line 24 and for addition ofcupric copper solution through line 25 to replace mechanical losses.Also from time to time, it may be desirable to adjust the pH of thesystem by addition of small amounts of hydrochloric acid, either by wayof makeup line 25 or at the regeneration zone 6, via line 26, to replacevaporization losses.

While the foregoing disclosure has related particularly to acontinuously operating process, it is likewise applicable to batchwiseoperation; also to the use of two consecutive reactors operated inseries for the oxidation of very refractory mercaptans, and suchembodiments are within the scope of our invention.

Advantages of this invention are illustrated by the following examples.The reactants and their proportions and other specific ingredients arepresented as being typical and should not be construed to limit theinvention unduly.

Ercample I Ditertiary octyl disulfide was prepared by the oxidation oftertiary octyl mercaptan in a manner similar to that shown in theaccompanying diagram. The solvent employed was toluene, and was used ina ratio of 3 partsjof toluene to 1 part of mercaptan. The coppersolution was pre1-:- pared by dissolving 14.8 wt. per cent cupricsulfate pentahydrate and 13.5 wt. per cent sodiuml chloride in water.The volume ratio of copper solution to mercaptan-toluene solution intheI reactor was maintained at 4.5:1. VThe charge rate of the mercaptansolution feed was 500: volumes per hour while the rate at which thecopper solution was circulated to the regeneration unit was 12,000volumes per hour. Thel product take-off rate was substantially the sameIas the mercaptan solution input; 500 volumes perI hour. The run wascarried out continuously for a period of 4 hours.

The product stream was washed with causticr stripped of toluene solventto be recycled, andi fractionally distilled under reduced pressure. Ayield of 98 per cent based on mercaptan feed was obtained. Theditertiary octyl disulfide was clear, pale yellow in color, and sweet tothe doctor test. Other properties were:

Density, gm./cc. at 28 C 0.9153 Refractive index, nl, 1.4998 Totalsulfur, weight per cent 21.6 Mercaptan sulfur, weight per cent 0.0

Tests were made on the copper solution at the beginning of this run andeach hour thereafter to determine oxidation potential and pH. Sampleswere removed from the recycle stream between the regenerating unit andthe reactor. Results of these tests were as follows:

Time (hrs.) Pogtial pH This data shows that after the third hour ofoperation an equilibrium is obtained and the pH and oxidation potentialstay relatively constant.

Example II A run was made using tertiary-dodecyl mercaptan as feed stockand toluene as the aromatic solvent, the method being essentially thesame as that described in Example I. The temperature in the reactor washeld at to 140 F. The product, ditertiary dodecyl disulfide, was

clear, light yellow in color, and had the following additionalproperties:

Density, g./cc. at 28o C 0,9158' Refractive index, 1tD20 1.5008 Totalsulfur, weight per cent 15.4 Mercaptan sulfur, weight per cent 0.17

Example III Boiling range at 50 mm. pressure, F 215-225 Density, g./cc.at 26 C v0.8998 Refractive index, 2 1.4838 Total sulfur, weight per cent33.2

' Example IV This example shows that itis uneconomical 4to try toprepare dialkyl disulfldes from low boils l ing mercaptamsiutiiizing an.aliphatic: hydrocarbomsolnent.. 'Iertiary1 butyla mercaptan was'. usedas; theemercaptan. feed. andi isooctanei was used as ther solvent; Qn:attempting to. oxdize'. the mercaptan toithe.corresponding disulfide,mostof 'the intermediate product. which.'v was` a. cuprous mercaptide;lprecipitated out aisl yellow crystals, thus, preventing the-.formationof the disulfide bythe reaoizicir ofi the. mercaptida with the copper'ion.

(Dur process. forf they manufacture` ofi dialkyl disuldes fromlow-molecular: weight mercaptans off. greatutility in. that: it'provides a method which. is; rapid; economicalg. andeasi-ly followed;and wherein the cuprous mercaptid'e,Y ordinarily insoluble:` inaliphatic. hydrocarbons, is kept. in solutiong. thus allowingsubstantially complete conuersimrof themercaptan charged toa dialkyldisuldei.

Althuughi processhas been described and exemplified im termszof itsLpreferred m'odi'ca.- tions, it is understeodithattvarious.minor changesmay. be made without departing from thespirit andscope of the disclosureand of` the claims.

We cl'aliin:

11A process, for. the, manufacture of. dialkyl disuldes from lowmolecular weight mercaptans whichmomprisesldissolving amercaptancontaining notlmor-e than 10-fcarbonratoms per moleculer inarr. aromatichydrocarbon selected from the group consisting of-benzene and alkylsubstituted benzenes, the-resulting. aromatic hydrocarbon solutionexclusive ofmercaptan containing atleast Souper. centaromatics and thevolume ratio of said solutionl to mercaptan being in the range ofZtl to-521; contacting atan elevated temperatureY the mercaptan-aromatichydrocarbon solution; with anoxidizing solution consistingAessentiallyrof an aqueollsouprio copper ionisolution in Whicl'r` theconcentrationofV cupric copper is: in the; range of`3' to 14 mol percent and the ratio of cupric copper ion solution to mercaptanaromatichydrocarbon solutionaisin therange-of kzflr'toi LQ: li sozasztosubstantially completely. oxidizersaict memaptanztthe. correspondingdialleyl. disulfide; continuously removing a minor portion of the thusformed dialkyltdisulde-aromatic hydrocarbon-cugino. copper. ion. mixtureto a separation. zone, and'removinatherefrom said aqueous` cupriocopper. ion solution; .`regenerating..said.v aqueouscupric copper ionsolution Y by changing cuprous` copper. thereinetocupric copper and re-Ycyclingsameto said :contacting recycling. amajorr pprtionxof saddialkyldisulde-arornatichydro.- carbon; separating the remainingmior portion.of said dialkyl disulde-aromatic hydrocarbon; recycling separatedAaromaticY hydrocarbon; andi recovering-said dialky-l-disuliide as aproduct of the-process.N

2f A process aceordingto claim 1 wherein said?- aromatic hydrocarbonisitoluene.

3,. A Vprocess accordingto claim l vWhereinregeneration o-saidcupricVVcopper ion solution` is eifected by passingjastreamofoxygen-containingji gasitherethrough:

4; A' process; for the `manufacture of dialkyl' 55' disuldes from lowrmolecular VWeight* mercaptansN whiclr comprisesv treatingK4 anaromatichydrois in the range of .1:1 .to 10:1 of a mercaptan with an oxidizingsolution consisting essentially oLannqneousi cupriocopper;ionesolutionV-the-aromatic ludrocarbmrsolutionirchisiveiofmercawSCF.

tarrcontaining atleastlo per cent aromatic's, the volume-ratio off saidsolution; to mercaptanl being 2:1v to. 5:1', said mercaptanf containingnot more than: about 1f2 carbon atoms per molecule; and recovering theycorresponding dialkyl disulfide from-saidtreating.

5t process for thel manufactureol diallyl.` disuifid'es from lowmolecular weight iriercaptan'si which comprises dissolving a mercaptancontaining. not morethan: l2lcarbon atoms per molecule in an. aromatichydrocarbon. of: the single ring type, the aromatic hydrocarbon.solution` exclusive' of mercaptancontaining. at. least 80fiper centaromatics, the: volume ratio of said. solution to mercaptan. beingi 2:1i to 5: 1.-, contacting. sai'dmericaptan-aromatic hydrocarbon solutionwith. al major portion of ans oxidizing solution consisting essentially.of ani aqueous cupric copper ion solution; in which the concentrationof. cupricoopper f isin, the range of 31to 14 mol per centandthe ratioof cupric copper ion solution to mercaptaninaromatic hydrocarbon mixtureis in therange of lltlf to 10:1V atan elevated temperature andsubstantially,k completely oxidizing said mercaptan toftheYcorresponding dialkyl disulfide therewith; separating'said aromatichydrocarbon con-- taining saiddialkyl disulde from said aqueous' cnpriccopper ion solution, and recovering saiddialkyl` disulide from saidaromatic y hydrocarbon as a product of the process.

6. Aprocessfor the manufacture ofV dialkyl di sulfide f-romlow molecularWeightmercaptans, which comprises dissolving a. rnercaptan containingnot.. more than 10 carbonatomsper molecule inan. aromatichydrocarbon-selected. from the group consistingof benzeneandealkylsubstitutedI benzenes in-a/volumefratio of mercaptan to.aromatic hydrocarbon in. the. range of 1:2 to l:5,. the concentration.` ofaromatic hydrocarbon ex-l clusive of" mercaptanY being. atleast 80 percent,`

contacting. the thus formed mercaptan-aromatic hydrocarbon. mix-turewithI an oxidizing solutionconsistingessentially.of an .aqueous cupriccopper ion. solution in a. volumeratio of. oupric copper ion solution to.mercaptan-aromatic hydrocarbon` solution inthe range of`1`z11to 10i: 1andat atemperature in the range .of 5i) to.200'F., said cupric copperconcentration being in the range ofv 3v to lflmol'per'c'ent',substantially completc'elyY oxidizing saidrnercaptan' to thecorresponding dialkyl disul'de' by means. `of said.' cupric copperV ionso.- lution,` continuously removing aA portion of. the dialky-lidisulfide-aromatic hydrocarbon-cupric'l copperiionzmixture from saidreaction zone to a separationizone wherein said-aqueous cupric copperion solution is. removed 'therefrom the faqueous cupric copper portionof said mixture removedfrom said reaction zone beingl inthe rangeof.about"50"t'o"200` volumes per volumeof'mercaptan-aromatic hydrocarbonintroduced to said reaction. zone,y regenerating said aqueous cupric.

`major portion of `sa`id dialkyl disulfide-aromatic disulfides `fromlow" molecular Weight mercaptans,4

Whiclicomprises fdissolving amercaptan'containinginotmore: than-101carbon 'atoms per. molecule' 75l-in an aromaticfhydrocarbbn"selected*from the' group consisting of benzene and alkyl substituted benzenes ina volume ratio of mercaptan to aromatic hydrocarbon in the range of 1:3to 1:4, the concentration of aromatic hydrocarbon exclusive of mercaptanbeing at least 80 per cent, contacting the thus formedmercaptan-aromatic hydrocarbon mixture with an oxidizing solutionconsisting essentially of an aqueous cupric copper ion solution in avolume ratio of cupric copper ion solution to mercaptan-aromatichydrocarbon solution in the range of 6:1 to 8:1 and at a temperature inthe range of 70 to 140 F., said cupric copper concentration being in therange of to mol per cent, substantially completely oxidizing saidmercaptan to the corresponding dialkyl disulfide by means of said cupriccopper ion solution, continuously removing a portion of the dialkyldisulde-aromatic hydrocarboncupric copper ion mixture from said reactionzone to a separation zone wherein said cupric copper ion solution isremoved therefrom, the aqueous cupric copper portion of said mixtureremoved from said reaction zone being in the range of 50 to 200 volumesper volume of the mercaptanaromatic hydrocarbon introduced to thereaction zone, regenerating said separated aqueous cupric copper ionsolution by passing an oxygen-containing gas therethrough, recyclingsaid regenerated cupric copper solution to said contacting, recycling amajor portion of said dialkyl disulfidearomatic hydrocarbon, lseparatingthe remaining minor portion of said dialkyl disuliide-aromatichydrocarbon containing one volume of dialkyl disulde per volume ofmercaptan charged, separating and recycling aromatic hydrocarbon, andrecovering said dialkyl disulfide as a product of the process.

8. A process according to claim 7 wherein the oxidation potential withinthe reaction zone is maintained between 375 and 500 millivolts asmeasured against saturated calomel.

9. A process according to claim 7 wherein said cupric copper ionsolution comprises an aqueous solution of cupric copper ion in thepresence of a chloride ion concentration equivalent to that of a 10 to20 mol per cent sodium chloride solution.

10. A process for the manufacture of ditertiary butyl disulfide whichcomprises dissolving tertiary butyl mercaptan in toluene in a volumeration of 1:3 to 1:4 respectively, the concentration of toluene in theresulting solution exclusive 10 of mercaptan being atleast 80 per cent,contacting the thus formed hydrocarbon mixture with an oxidizingsolution consisting essentially of an aqueous cupric copper ion solutionin a volume ratio of cupric copper ion solution to mercaptanaromatichydrocarbon mixture in the range of 6:1 to 8:1 and at a temperature inthe range of to 140 F., said cupric copper concentration being in therange of 5 to 10 mol per cent, substantially completely oxidizing saidmercaptan to the corresponding dialkyl disulfide by means of said cupriccopper ion solution, continuously removing a portion of the ditertiarybutyl disulde-toluene-cupric copper ion mixture from said reaction zoneto a separation zone, the aqueous cupric copper portion of said mixtureremoved from said reaction zone being in the range of 2O to 30 volumesper volume of the teritary butyl mercaptan and toluene introduced to thereaction zone, separating the ditertiary butyl disulfidetoluene mixturefrom said aqueous cupric copper ion solution, regenerating saidseparated aqueous cupric copper ion solution by passing anoxygencontaining gas therethrough, recycling said regenerated cupriccopper solution to said contacting, recycling a major portion ofsaidditertiary butyl disulfide-toluene mixture, separating the remainingminor portion of said ditertiary butyl disulde-toluene mixturecontaining one volume o1 ditertiary butyl disulfide per volume ofmercaptan charged, separating and recycling toluene, and recovering saidditertiary butyl disuliide as a product of the process.

WALTER A. SCHULZE. WILLIE W. CROUCH.

References Cited in the iile of this patent UNITED STATES PATENTS NumberName Date 2,378,092 Messmore et al June 12, 1945 2,415,851 Schulze et alFeb. 18, 1947 2,421,545 Crouch v June 3, 1947 2,503,644 Warner et alApr. 11, 1950 FOREIGN PATENTS Number Country Date 435,113 Great BritainSept. 16, 1935 OTHER REFERENCES Birch et al., Ind. Eng. C'o., vol. 28,No. 6, June 1936, page 668. Slagle et al., ibid., vol. 24, No. 4, pages448-451.

1. A PROCESS FOR THE MANUFACTURE OF DIALKYL DISULFIDES FROM LOWMOLECULAR WEIGHT MERCAPTANS WHICH COMPRISES DISSOLVING A MERCAPTANCONTAINING NOT MORE THAN 10 CARBON ATOMS, PER MOLECULE IN AN AROMATICHYDROCARBON SELECTED FROM THE GROUP CONSISTING OF BENZENE AND ALKYLSUBSTITUTED BENZENES, THE RESULTING AROMATIC HYDROCARBON SOLUTIONEXCLUSIVE OF MERCAPTAN CONTAINING AT LEAST 80 PER CENT AROMATICS AND THEVOLUME RATIO OF SAID SOLUTION TO MERCAPTAN BEING IN THE RANGE OF 2:1 TO5:1; CONTACTING AT AN ELEVATED TEMPERATURE THE MERCAPTAN-AROMATICHYDROCARBON SOLUTION WITH AN OXIDIZING SOLUTION CONSISTING ESSENTIALLYOF AN AQUEOUS CUPRIC COPPER ION SOLUTION IN WHICH THE CONCENTRATION OFCUPRIC COPPER IS IN THE RANGE OF 3 TO 14 MOL PER CENT AND THE RATIO OFCUPRIC COPPER ION SOLUTION TO MERCAPTANAROMATIC HYDROCARBON SOLUTION ISIN THE RANGE OF 1:1 TO 10:1 SO AS TO SUBSTANTIALLY COMPLETELY, OXIDIZESAID MERCAPTAN TO THE CORRESPONDING DIALKYL DISULFIDE; CONTINUOUSLYREMOVING A MINOR PORTION OF THE THUS FORMED DIAKLYL DISULFIDE-AROMATICHYDROCARBON-CUPRIC COPPER ION MIXTURE TO A SEPARATION ZONE AND REMOVINGTHEREFROM SAID AQUEOUS CUPRIC COPPER ION SOLUTION; REGENERATING SAIDAQUEOUS CUPRIC COPPER ION SOLUTION BY CHANGING CUPROUS COPPER THEREIN TOCUPRIC COPPER AND RECYCLING SAME TO SAID CONTACTING; RECYCLING A MAJORPORTION OF SAID DIALKYL DISULFIDE-AROMATIC HYDROCARBON; SEPARATING THEREMAINING MINOR PORTION OF SAID DIALKYL DISULFIDE-AROMATIC HYDROCARBON;RECYCLING SEPARATED AROMATIC HYDROCARBON; AND RECOVERING SAID DIALKYLDISULFIDE AS A PRODUCT OF THE PROCESS.